For the past few games, Liz O’Sullivan has been forced to observe her New Canaan girls lacrosse teammates from the bench, sidelined by a thumb injury incurred during a practice.

It was going to take a lot more than that, however, to keep the senior co-captain out of the FCIAC tournament.

With O’Sullivan back between the pipes, senior co-captain Kelly Armstrong ruling the day on draw controls, and the offense hitting on all cylinders, the Rams steam-rolled over the Greenwich Cardinals, 14-6, in the FCIAC semifinals Monday at Dunning Field.

For O’Sullivan, who made six saves, getting back into the swing of things on a big stage was exhilirating.

“I’ve been watching my team playing for a week and a half,” O’Sullivan said. “And as a senior going out in the FCIAC tournament, which we haven’t won since the 90s, I was just so excited to be back for my team and help us bring home that ship finally.”

“We haven’t been to the FCIAC championship in a couple of years so it feels so good to be back on track. We’re really excited for that game.”

The FCIAC championship will truly be a clash of lacrosse titans, as rivals Darien and New Canaan, the top two seeds, square off at 4 p.m., Friday, at Brien McMahon High School in Norwalk. Darien, the No. 1 seed, is 16-1 after defeating Danbury 22-9 in the semifinals, while New Canaan, the No. 2 seed, is 17-1.

Although both New Canaan and third-seeded Greenwich (14-4) came in with glittering records this season, any possible dramatic spark fizzled out in the first 15 minutes, as the Rams dominated the draws and time of possession while scoring the first six goals.

Elizabeth Miller began the onslaught with a goal just 48 seconds into the game, senior co-captain Olivia Hompe followed with the first of her four tallies at 3:51, and freshman Katie DeMarino netted a third goal at 7:27.

Senior Brianna McEwan added the fourth goal, followed by two more from DeMarino and Hompe for a 6-0 lead which left the Cardinals in the dust.

“We had a good game plan and they did a good job executing it,” head coach Kristin Woods said. “Every single person came out focused today and that’s what we need to win big games. Our goal was to play our game and focus on the things we can control and they did a great job of that today.

“We won the first six draws and that’ll get you,” she added.

Greenwich’s Carolyn Paletta broke the Cards’ slide with 10:33 on the clock, but New Canaan closed the half on a 3-1 run, with two goals from Miller and one from Isabel Taben for a 9-2 advantage at the break.

While the offense was unstoppable, the defense was unbreakable.

O’Sullivan and the defensive unit of Armstrong, Wheatley Raabe, Lizzie Burke, and Abigail Sawbini, among others, was on its game.

“Liz played very well today and she really stepped up,” Woods said of her goalie. “She had a few weeks off but she was excited to get back in there. Sometimes rest is the best thing for you because you get re-energized.”

O’Sullivan said the play of the midfielders kept the heat on Greenwich, while allowing the defense to play a bit looser.

“The midfield took a ton of pressure off D,” O’Sullivan said. “Sometimes when a team is winning a bunch of draw controls in a row, it’s hard. You have to play really reserved because you can’t afford fouls or to give any slides up. So it really did allow us to push the envelope and we got to take more risks, which paid off in the end.”

Any thoughts of a second-half rally by the Cards were quickly put to rest when the Rams scored three unanswered goals in less than two-and-a-half minutes for a 12-2 lead.

The advantage was up to 11 at 14-3 with 13 minutes remaining when the Rams went into full possession mode, content to run time off the clock. Greenwich managed to score the final three goals, but it was too little, too late.

Hompe finished with a game-high four goals with one assist, while Miller had a hat trick. DeMarino, Taben, and McEwan each scored twice, Sami Stewart scored once, and Bea Eppler had an assist. New Canaan was 12-5 on draws, with Armstrong winning six and Burke taking three.

For Greenwich, Paletta led the offense with three goals, while Emma Christie, Sophie Waine and Sarah Rider each scored once.

After hitting a low point with a loss on a dreary night in last year’s FCIAC semifinals, the Rams managed to find a sunny day in the semis this time around.

“This group, especially the seniors that we have, really wanted to get back to the FCIAC championship,” Woods said. “And they’re ready to go.”